The invention relates to a method for converting hydrates buried in the water bottom into a marketable hydrocarbon composition.
Such a method is known from US patent application US 2008/0088171. In the known method a mixture of methane hydrates and mud is prepared with an underwater mining assembly and then brought to a methane dome near the water surface by a series of buckets that are attached to a pair of rotating chains. The methane hydrate is collected and allowed to decompose into methane and water in the methane dome from where the methane is removed to produce liquefied natural gas or synthetic liquid fuels.
A disadvantage of the known method is that methane hydrates are generally present at water depths of more than 1 kilometer, such that very long chains and a large amount of buckets are required to lift the mixture of methane hydrates and mud to the water surface, so that the known method requires costly and heavy equipment, which makes the known bucket dredging method unsuitable and uneconomic for use at large water depths.
Other underwater hydrate excavation methods are known from U.S. Pat. No. 6,209,965, US patent application US2003/0136585, International patent application WO98/44078 and Chinese patent application CN101182771.
It is an object of the present invention to provide an improved method for producing a marketable hydrocarbon composition from a hydrate deposit buried in the water bottom, which is economic and suitable for use at large water depths.